In line with the recent increase in the importance of detecting or quantifying chemical substances and biological substances such as DNA (Deoxyribo Nucleic Acid), enzyme, antigen, antibody, protein, virus, cells, and the like in the field of medical care, health, food product, development of medicine, and the like, various biochips and microchemical chips (hereinafter collectively referred to as a microchip) that allow measurement thereof in a simplified manner have been proposed.
A microchip has many advantages in that a series of experiments and analytical operations carried out at laboratories can be performed within a chip that is approximately from several cm to 10 cm square and from several mm to several cm in thickness and accordingly only a small amount of specimen and reagent is required, reduction in cost is achieved, a reaction speed is fast, tests or analysis can be performed with high throughput, and test results can be obtained immediately at the site where the specimen has been collected.
A microchip has a fluid circuit therein. The fluid circuit is mainly constituted, for example, of such sites as a liquid reagent receptacle unit for holding a liquid reagent to be mixed with or caused to react to a specimen (for example, blood) to be tested or analyzed, or for treating the specimen, a measurement unit for measuring the specimen or the liquid reagent, a mixing unit for mixing the specimen and the liquid reagent, and a detection unit for testing or analyzing the liquid mixture, as well as minute channels appropriately connecting these sites.
In use, a microchip is typically mounted on an apparatus that can apply centrifugal force to the chip. By applying centrifugal force to the microchip in an appropriate direction, measurement of a specimen (or a specific component in the specimen) and/or a liquid reagent, mixing of the specimen (or the specific component in the specimen) and the liquid reagent, as well as introduction of the obtained liquid mixture to the detection unit, or the like, can be carried out. It is noted that such treatment as transfer from one site to another site, measurement, and mixing of various liquids (a specimen, a specific component in the specimen, a liquid reagent, or a mixture or a reactant of two or more types thereof, and the like) performed within a microchip may hereinafter be referred to as “fluid treatment”.
For example, Japanese Patent Laying-Open No. 2009-133805 (PTD 1) discloses a microchip suitably used as a blood test chip. The microchip disclosed in this document includes a hemocyte separation unit for separating a hemocyte component from whole blood introduced within the microchip and extracting a plasma component as a part of a fluid circuit, and allows a test using only the plasma component.